Overview

Bronchiectasis is irreversible, abnormal dilatation of the bronchi.
[1] Common etiologies for bronchiectasis are congenital abnormalities, recurrent infection, and airway obstruction. The tethering effect of pulmonary fibrosis can also dilate the airways, causing traction bronchiectasis.
[2, 3] Involved bronchi are dilated, inflamed, and easily collapsible, resulting in airflow obstruction and impaired clearance of secretions. Bronchiectasis typically presents with cough, sputum production, and airway obstruction,
[4] and in severe cases, massive hemoptysis can lead to death.
[1]

In bronchiectasis, damaged epithelium impairs removal of mucus and increases the risk of infection by pathogens such as Pseudomonas aeruginosa, Haemophilus, Aspergillus fumigatus, and nontuberculous mycobacteria.
[5]

Bronchiectasis is a final common pathway for many diseases with diverse fundamental causes. Knowledge of the root cause of bronchiectasis in a particular patient is more helpful for treatment than an understanding of the generic subject of bronchiectasis. Bronchiectasis is associated with a wide range of disorders, but it usually results from necrotizing bacterial infections, such as infections caused by the Staphylococcus or Klebsiella species or Bordetella pertussis. Unfortunately, in about half the cases, the specific cause of bronchiectasis remains undetermined.
[6]

Hemoptysis is common and may occur in as many as 50% of patients. Episodic hemoptysis with little to no sputum production (dry bronchiectasis) is usually a sequela of tuberculosis. However, massive hemoptysis may occur; bleeding usually originates in dilated bronchial arteries, which contain blood at systemic (rather than pulmonary) pressures.

Preferred examination

Diagnosis of bronchiectasis is based on a clinical history of daily viscid sputum production and characteristic computed tomography (CT) scan findings.
[1, 4] (See the images below.)

Chest radiography is usually the first imaging examination, but the findings are often nonspecific, and the images can appear normal.
[7] High-resolution computed tomography (HRCT) scanning was once the imaging modality of choice for assessing the possibility of bronchiectasis and its extent (see the images below). HRCT scanning also helped radiologists evaluate the surrounding tissue for other pathology, such as malignancy.
[8]

Until the advent of HRCT scanning, bronchography was the classic modality used for imaging bronchiectasis. Bronchography is performed by instilling an iodine-based contrast material via a catheter or bronchoscope, but it is rarely, if ever, performed today, as CT scanning has replaced it as the diagnostic modality of choice. HRCT scanning is noninvasive and has a sensitivity of 96% and a specificity of 93%.
[9]

Volumetric multidetector CT acquisition of the chest is now the preferred examination for the diagnosis of bronchiectasis. Compared with the previous criterion standard of high-resolution CT (HRCT), volumetric CT offers several improvements.
[10, 11] Equivalent reconstructed HRCT images can be generated from the volumetric data set without additional scanning.
[12] In addition, volumetric CT allows multiplanar reconstructions, which improve assurance of diagnosis, at least partially by permitting better assessment of absence of tapering of bronchi.
[13, 14] By including the entire lung volume, volumetric CT increases the sensitivity of detection for smaller regions of bronchiectasis and permits more confident exclusion of the diagnosis.
[10, 11, 14, 15] Pulmonary vessels and foci of mucous plugging can be differentiated from lung nodules with volumetric chest CT, avoiding unnecessary repeat examinations.
[11, 14]

Volumetric CT can be acquired in a single breath-hold. This reduces breathing artifact, which can be confused with bronchiectasis.
[10, 16] Since the initial demonstration of improvement in diagnostic accuracy with multidetector row CT, CT technology has progressed remarkably with the addition of more detectors and substantial improvements in scanner speed. These improvements have solidified the superiority of volumetric CT as the preferred examination.

Although volumetric CT has numerous advantages, the radiation dose is higher. Radiation dose can be mitigated by several techniques.
[17] This is particularly important in pediatric patients, because of their increased radiation sensitivity. Radiologists should use modified protocols especially suited for children.
[17, 18] Limited HRCT imaging could be appropriate in some patients for follow-up imaging in order to reduce the radiation dose.

The premise of a preferred examination for bronchiectasis implies that the requesting physician already knows the diagnosis, but bronchiectasis is only definitively diagnosed on chest CT. Bronchiectasis could be the suspected diagnosis triggering the request. However, as a practical matter, physicians request examinations in response to patient presentations, relying on the radiologist to protocol the examination to differentiate among possible conditions that could present similarly.
[19, 20, 21, 22, 23] Most chest CT protocols are likely to demonstrate the findings of bronchiectasis, if present. Moreover, unsuspected bronchiectasis is often diagnosed on chest CT obtained for unrelated reasons. Once bronchiectasis is diagnosed, follow-up chest CT can be tailored for optimal assessment and follow-up of bronchiectasis, along with any other conditions.

The HRCT scan shows thick-walled, slightly ectatic bronchi. The patient has cystic fibrosis, which was diagnosed and treated since childhood.

This HRCT scan through the right upper lobe demonstrates bronchiectasis. Despite conventional antibiotic treatment, the patient continued to be symptomatic. Eventually, she underwent bronchoscopy, and sampled cultures grew Mycobacterium avium-intracellulare complex.

Clinical details

The classic clinical presentation for a patient with bronchiectasis is intermittent or daily, often purulent, sputum production. This is often accompanied by other symptoms such as dyspnea, fatigue, weight loss, chest pain, hemoptysis, and clubbing of the fingers.
[24, 25, 26, 27, 28] Patients may develop respiratory failure or right heart failure.
[24] The classic clinical presentation should prompt further investigation by chest CT.

However, bronchiectasis is a morphologic pattern, which is typically identified by chest CT. It is the final common pathway for many fundamental causes, which have a broad range of presentations. A more specific approach is to identify the basic cause of bronchiectasis, if possible, and consider the clinical details of that cause.

Pathophysiology

Bronchiectasis is not caused by a single factor, but is a complex interplay between repeated inflammation and a defective immune response to inflammation.
[29] Many congenital or acquired abnormalities can prevent normal airway defense and repair, resulting in infection. If the initial reaction to infection is ineffective, the immune response is increased and prolonged, potentially causing a vicious circle of bronchial injury and increased inflammation that leads to bronchiectasis.
[30] Bronchial damage includes variable amounts of bronchomalacia or fibrosis and disturbance of mucociliary function.

Examples of defective cellular or humoral immunity that predispose to bronchiectasis occur all along the immune response pathway. King et al found that adult patients with bronchiectasis had significantly lower levels of immunoglobulin G3 (IgG3), B-cell lymphocytes, and T-helper lymphocytes.
[31] In about one third of adult bronchiectasis patients, King et al also found a significantly diminished neutrophil oxidative burst.
[31] Numerous examples of diminished immunity have been cited to account for susceptibility to bronchiectasis, including primary immune deficiencies, positive HIV status, female sex, rheumatoid arthritis, and ulcerative colitis.
[6, 32, 33, 34, 35]

Allergic bronchopulmonary aspergillosis is caused by an abnormal immune response to Aspergillus fumigatus, which results in bronchiectasis.
[36] Infection can be the inciting cause for bronchiectasis. Viral infections associated with bronchiectasis include pertussis, measles, whooping cough, and influenza.
[37, 38] Bacterial infections, such as Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, and typical and atypical tuberculosis, have been cultured from patients with bronchiectasis.
[29, 37, 38, 39]

Ordinarily, pathogens are trapped by bronchial mucus and removed by the mucociliary elevator. Some patients, such as patients with cystic fibrosis or Young syndrome, have an altered mucous viscosity that impedes effective mucous removal.
[40, 41] Others, such as patients with primary ciliary dyskinesia, have a defective anatomic mechanism for mucous clearance.
[42, 43]

Altered anatomy can play a role in recurrent infections. A congenital abnormality that affects normal anatomy, such as communicating bronchopulmonary foregut malformation, tracheal bronchus, or accessory cardiac bronchus can precipitate bronchiectasis.
[44] Patients with Williams-Campbell syndrome have a congenital cartilage defect that predisposes them to bronchiectasis,
[45] while patients with Mounier-Kuhn syndrome (tracheobronchomegaly) have deficient tracheobronchial smooth muscle and elastic fibers.
[46]

Inhalational lung injury from smoke or other noxious gases often is the initial event in the cycle ending in bronchiectasis.
[47] Central bronchial obstruction can be caused by foreign body, broncholith, tumor, or lymphadenopathy, leading to bronchiectasis.
[48, 49, 50] Patients with end-stage fibrosis can develop traction bronchiectasis and bronchiolectasis. Common examples include usual interstitial pneumonitis, tuberculosis, sarcoidosis, and radiation fibrosis. High negative pleural pressures and increased elastic recoil in pulmonary fibrosis interact to enlarge the bronchi.
[51] The dilated bronchi are typically distorted with a beaded appearance.
[52] Depending on the distribution of fibrosis, traction bronchiectasis can be regional or widespread. Traction bronchiectasis is restricted to the areas of end-stage fibrosis and particularly affects peripheral bronchi, which lack cartilage support.
[51]

Epidemiology

A review of nontuberculous mycobacteria-associated hospitalizations showed a significant upward trend with increasing age for males and females.
[53] In adults, the prevalence of bronchiectasis trends upward with increasing age.
[54, 55] The prevalence of bronchiectasis in patients aged 65 years and older has increased over time, possibly related to improved diagnosis and/or access to care.
[56] Weykert et al used a retrospective cohort design to estimate the prevalence of bronchiectasis in US adults.
[54] They found a prevalence of bronchiectasis ranging from 4.2 cases per 100,000 persons (18-34 yr) to 271.8 cases per 100,000 persons (75 yr and older).
[54]

Contrary to the case in the Western world, bronchiectasis is regarded as common in the East, though prevalence statistics are sparse.
[57] Although the prevalence of pediatric bronchiectasis has generally been declining in the more developed world, numerous regional studies suggest that pediatric bronchiectasis remains a significant problem in the developing world.
[58] Chang et al found a particularly high prevalence of bronchiectasis in aboriginal children aged 15 years and younger in Central Australia of 14.7 cases per 1,000 persons.
[59] In a health screening program for adults in Seoul, Korea, the prevalence of bronchiectasis was 9.1%.
[60]

For whites, cystic fibrosis is the most common life-threatening recessive genetic problem.
[61] Cystic fibrosis occurs in about 1 in 3,200 white live births; 1 in 15,000 African-American live births; and 1 in 31,000 Asian-American live births.
[61] In a University of Chicago study of 106 bronchiectasis patients of a diverse US population, bronchiectasis attributable to rheumatoid arthritis occurred more frequently in African-Americans than European-Americans, while bronchiectasis related to hematologic malignancy occurred more frequently in European-Americans than in African-Americans.
[62] Hispanic-Americans had positive sputum culture for P aeruginosa more often than the other ethnic groups in that study.
[62] A review of bronchiectasis in Medicare beneficiaries determined that for patients who had one chest CT scan, Asians were 2.5 times more likely to have bronchiectasis than whites and 3.9 times more likely than blacks.
[56] A study of nontuberculous bronchiectasis in Medicare beneficiaries found the prevalence in blacks was half that of whites and the prevalence in Asians/Pacific Islanders was twice that of whites.
[63]

Overall, bronchiectasis unrelated to cystic fibrosis occurs more frequently and is more severe in women.
[35] Although cystic fibrosis has an equal distribution between males and females, the diagnosis may be delayed in females, which could explain why females tend to die younger.
[64] Rheumatoid arthritis,
[65] sarcoidosis,
[66] and Sjögren syndrome all have a female predominance and predispose to bronchiectasis. Mycobacterial tuberculosis occurs more frequently in males.
[67, 68] Mycobacterium avium complex has generally been found more frequently in older women.
[63, 69, 70, 71] Women in the United States are diagnosed with nontuberculous mycobacterial disease 1.4 times more frequently than men among Medicare patients older than 65 years.
[63] With various study methodologies and geographic locations, sex ratios for nontuberculous mycobacterial disease can vary considerably.
[72]

Mortality/morbidity

Pediatric bronchiectasis in the developing world carries a higher rate of morbidity and mortality, at least partially related to poorer nutrition.
[58] Hemoptysis and chronic respiratory failure are also more common in the developing world.
[58]

Quality of life can be assessed by the St George’s Respiratory Questionnaire or the Leicester Cough Questionnaire.
[73] Frequency of exacerbations of symptoms can be used to judge effectiveness of treatment, and exercise capacity can be evaluated by the incremental shuffle walk test or the 6-minute walking test.
[73]

Patients with cystic bronchiectasis are at risk for developing a mycetoma within a dilated bronchus. Hemoptysis is common and may occur in as many as 50% of patients. Episodic hemoptysis with little to no sputum production (dry bronchiectasis) is usually a sequela of tuberculosis. However, massive hemoptysis may occur; bleeding usually originates in dilated bronchial arteries, which contain blood at systemic (rather than pulmonary) pressures.
[76]

Limitations of techniques

In general, if a volumetric study of the chest is obtained without significant motion artifact in an adult patient, there should be no important limitation to the identification or exclusion of bronchiectasis. However, the operational definition of bronchiectasis is "irreversible, abnormal dilatation of the bronchi."
[7, 8] Reversible bronchial dilatation has been identified rarely in adults.
[80] Gaillard et al reviewed follow-up CT examinations in 22 non–cystic fibrosis pediatric patients with bronchial dilatation. In 6 patients, the bronchial dilatation resolved completely and in 8 patients there was improvement.
[81] For patients with complete reversal of bronchial dilatation, a single study would be insufficient.

Bronchoscopy is not helpful in diagnosing bronchiectasis, but it may be used to identify underlying abnormalities, such as tumors and foreign bodies.

Chest radiographs may be negative in patients with minor to moderate disease. Many abnormal radiographic findings may be nonspecific, and confirmation using volumetric CT scanning may be required.

Bronchography is rarely indicated because it is invasive and is associated with allergic reactions to the contrast material. Bronchography also carries the risk of acute bronchoconstriction.

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Radiography

Chest radiography helps to identify serious disease, and it was once the standard imaging modality.
[2] However, the radiographs may depict no abnormalities, or the findings may be nonspecific in patients with less-severe disease.
[3]

Various abnormal radiographic findings have been described as follows (see the images below)
[82, 83, 84] :

Parallel line opacities (tram tracks) caused by dilated, thickened bronchi are seen along their length

Ring opacities or cystic spaces as large as 2 cm in diameter resulting from cystic bronchiectasis, sometimes with fluid levels

Loss of definition of the central bronchi and vessels, related to central interstitial lung disease and retained secretions

Traction bronchiectasis occurs with pulmonary fibrosis. In pulmonary fibrosis, honeycombing and distortion can be visible radiographically. However, the radiographic diagnosis of traction bronchiectasis can be difficult, unless the surrounding lung is opacified.
[83] Patients with bronchiectasis are at increased risk for pneumonia. Chest radiography can be used for detection and follow-up of pneumonia associated with bronchiectasis.

Bronchography

Bronchography was the investigation of choice for bronchiectasis from its introduction in 1922 until the advent of HRCT scanning in the mid-1980s. Currently, bronchography is rarely used. Bronchography is performed by instilling contrast material via a catheter or bronchoscope under fluoroscopic control and conventional radiographic imaging. The procedure is unpleasant for the patient and is also associated with temporary impairment of ventilation, as well as allergic and foreign body reactions to the contrast medium. In addition, interpretation of bronchographic images is difficult, owing to underfilling and retained secretions.

Degree of confidence

The accuracy of conventional radiographic findings in the diagnosis of bronchiectasis is unknown, because the findings are variable and nonspecific and depend on the severity and extent of the bronchiectasis. However, the severity of disease as seen on conventional radiography and HRCT scans shows good correlation. Chest radiographic findings may be normal or nonspecific in patients with less severe disease. The prevalence of signs of bronchiectasis at radiography correlates with the severity of bronchiectasis at HRCT, although radiography is less sensitive and less specific.
[85]

False positives/negatives

Many conventional radiographic findings are nonspecific and can be seen in patients with idiopathic pulmonary fibrosis, sarcoidosis, histiocytosis X, rheumatoid lung, and other chronic interstitial lung disorders.

If bronchiectasis is detected radiographically, chest CT is appropriate for categorization of extent and morphologic severity.

On axial images, in cylindrical bronchiectasis, bronchi coursing horizontally are seen as parallel lines, and vertically oriented bronchi are seen as circular lucencies that are larger than the adjacent pulmonary artery (signet-ring appearance). (See the image below.)

This HRCT scan in a 13-year-old female shows left lower lobe bronchiectasis, secondary to tuberculosis.

Degree of confidence

Except for extremely obese patients and examinations compromised by motion, volumetric imaging of the chest provides a very high degree of confidence to confirm or deny the diagnosis of bronchiectasis. HRCT scanning has a sensitivity of 96% and a specificity of 93%,
[9] as compared with bronchography.

Some patients without bronchiectasis have a 1.49:1 bronchus-to-artery ratio; therefore, the ratio is reliable only if it is greater than 1.5. If the ratio is less than 1.5, other signs, such as bronchial wall thickening and lack of tapering, should be present for the diagnosis of bronchiectasis.

Bronchial measurements may vary with the use of different window levels and window widths.
[39] Bronchial wall thickening is optimally seen with wide window width, such as 1000, and a low window level, such as -700 HU. Aritfactual wall thickening can be produced by changing window width.
[40] A bronchial wall thickening finding is not specific and is also seen in patients with asthma and smokers. Bronchiectasis occurs frequently in smokers with chronic obstructive pulmonary disease (COPD). In a quantitative CT study of patients with bronchiectasis who smoked, the BA ratio (bronchial lumen and adjacent artery), wall thickness, and wall area percent were significantly greater for whole lung and 4th-6th airway generations.
[89]

False positives/negatives

The variability of the bronchus-to-artery ratio at high altitudes and in patients with pulmonary hypertension may result in an overdiagnosis because of vasoconstriction in these conditions. The bronchial diameter relative to the adjacent pulmonary artery also increases with increasing altitude.
[94]

In patients with consolidation, dilated bronchi may not be seen. Cardiac and respiratory artifacts may obscure the results or mimic subtle bronchiectasis in the left lower lobe. Rarely, histiocytosis X and cavitating pulmonary masses mimic cystic bronchiectasis. Traction bronchiectasis occurs in patients with interstitial fibrosis and results from fibrous tethering of the bronchial wall. Rather than a primary bronchial abnormality, the bronchiectasis is caused by tethering and traction.

The patient’s age should be considered, since the bronchoarterial ratio increases with age.
[86] In rare instances in adults, but more frequently in pediatric patients, bronchiectasis can be reversible.

A dilated, cystic bronchus should be distinguished from a bulla, since a bronchial cyst has a perceptible wall, while a bulla does not.

Magnetic Resonance Imaging

MRI can be used to find bronchial wall thickening and dilatation of central bronchi, but spatial resolution limits assessment of smaller airways, such as third to fourth generation.
[95] Different sequences, including fast breath–hold acquisition techniques and very short echo-time, are increasingly used for better pulmonary detail.
[96, 97]

While volumetric CT remains the primary mode of assessment for bronchiectasis in adults, for cystic fibrosis patients and for young patients who may need repeated follow-up examinations, MRI yields useful information.

Teufel et al compared HRCT and 1.5-Tesla MRI using a very short echo time in 51 patients with cystic fibrosis. For these patients, both CT and MRI were able to detect bronchiectasis, mucous plugging, and peribronchial thickening, with MRI strongly correlating with the CT findings.
[87] Montella et al compared chest MRI with HRCT in 50 non–cystic fibrosis pediatric patients, and both modalities demonstrated bronchiectasis in approximately 72% of those subjects. Other findings in chronic pediatric lung disease were also assessed, with results supporting the use of chest MRI as a reasonable alternative to CT.
[98]

Although CT has better spatial resolution and shows morphology in more detail than MRI, MRI is superior for assessment of functional changes of altered hemodynamics and perfusion.
[95] ]
[9] Helium-3 (3He) MRI may be used for evaluation of pulmonary ventilation and function.
[99]

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Nuclear Imaging

Patients with bronchiectasis can suffer from chronic productive cough, recurrent infections, and hemoptysis. V/Q scanning can be useful in determining whether surgical resection is appropriate therapy, especially for hemoptysis. In one series, 23 of 66 patients treated surgically had hemoptysis as a symptom. V/Q scanning demonstrated undiminished perfusion in cylindrical bronchiectasis, but areas of cystic or mixed cystic and cylindrical bronchiectasis showed perfusion defects. If a patient has a scan showing less than 10% perfusion of a bronchiectatic region, those patients can benefit from surgical resection of that nonfunctional region.
[100]

The purpose of a V/Q scan is to determine perfused versus nonperfused areas of lung rather than to make a diagnosis of bronchiectasis. Different diseases can cause nonperfused areas of lung, so V/Q is used in conjunction with CT or MRI.

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Angiography

Hemoptysis is symptomatic of a potentially life-threatening condition and warrants urgent and comprehensive evaluation of the lung parenchyma, airways, and thoracic vasculature.

Multidetector-row CT angiography permits noninvasive, rapid, and accurate assessment of the cause and consequences of hemorrhage into the airways and helps guide subsequent management.
[21, 101] The combined use of thin-section axial scans and more complex reformatted images allows clear depiction of the origins and trajectories of abnormally dilated systemic arteries that may be the source of hemorrhage and that may require embolization.

The vasculature, pulmonary parenchyma, and airways can be assessed with Multidetector CT angiography. In disorders with chronic lung inflammation, including bronchiectasis, abnormal collateral systemic vessels form in the affected parts of the lung. These collateral bronchial arteries appear as tortuous vessels and can bleed. Occasionally, nonbronchial systemic arteries or pulmonary arteries bleed. Multiplanar reformatted images are used for identifying the origins and courses of these vessels.

Bronchiectasis, chronic bronchitis, lung malignancy, tuberculosis, and chronic fungal infection are some of the most common underlying causes of hemoptysis and are easily detected with CT angiography.

Results from multidetector CT angiography can be used to direct therapeutic angiography for bronchial or pulmonary arterial embolization or surgical resection.

Occasionally, an examination is limited by artifact from patient motion, data depletion from a very large patient, or timing of contrast bolus. Otherwise, multidetector row CT usually demonstrates the vasculature and the pulmonary parenchyma well.

In a series of 22 patients, using 16-detector row CT, bronchial (100%) and nonbronchial (62%) arteries causing hemoptysis were visible, with most traceable throughout their length.
[102] Substantial technological advances in CT since then allow more detailed visualization.

A 27-year-old man diagnosed with reactive airway disease as a child was examined because of frequent respiratory infections. This high-resolution computed tomography (HRCT) scan through the upper lungs shows extensive bronchiectasis. The sweat test was positive, and cystic fibrosis was diagnosed.

A close-up radiograph of the left upper lung in a 31-year-old woman with chronic cough since childhood shows nodules in the left upper lung; the right upper lung was similarly involved.

The HRCT scan shows thick-walled, slightly ectatic bronchi. The patient has cystic fibrosis, which was diagnosed and treated since childhood.

A 65-year-old woman was examined for chronic cough. The lateral chest radiograph shows hyperinflation and accentuation of the central bronchial interstitium.

This HRCT scan through the right upper lobe demonstrates bronchiectasis. Despite conventional antibiotic treatment, the patient continued to be symptomatic. Eventually, she underwent bronchoscopy, and sampled cultures grew Mycobacterium avium-intracellulare complex.

A 54-year-old asymptomatic woman with a history of tuberculosis was referred for preoperative chest radiography. The radiograph shows tracheal deviation to the right, an elevated minor fissure, and linear lucencies in the partially atelectatic right upper lung; these findings indicate bronchiectasis.

This lateral chest radiograph shows a partially atelectatic right upper lobe (same patient as in the previous image). The patient has cicatricial tuberculous bronchiectasis.

HRCT scan in a 75-year-old man with cystic bronchiectasis, right worse than left lower lobes.

This HRCT scan in a 13-year-old female shows left lower lobe bronchiectasis, secondary to tuberculosis.

This HRCT scan demonstrates findings of fluid-filled dilated bronchi in the left lower lobe of a 65-year-old man.

This magnified view of the right upper lobe in a 25-year-old male with cystic fibrosis shows tram tracks and rings, reflecting bronchial thickening. Dilated bronchi filled with mucus are seen as branching tubular opacities.

Axial image from volumetric CT of a 25-year-old male with cystic fibrosis shows thick, dilated bronchi, some with mucus plugging.

Coronal reconstruction from volumetric CT of a 25-year-old male with cystic fibrosis shows thick bronchial walls and dilatation as well as areas of mucous plugging, worst in the right upper lobe.